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1.
R. Riahi P. Teulet Y. Cressault A. Gleizes Z. Ben Lakhdar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,49(2):185-192
A method is presented to calculate the radiative transition probabilities and the radiative recombination rate coefficients
between electronic molecular states. Total transition probabilities are determined from vibrational transition probabilities
without considering the detailed rotational structure of the molecular electronic states. Radiative recombination rate coefficients
are obtained from the computation of vibrational photo-ionisation cross sections. Concerning spontaneous emission, Lyman (B
→ X) and Werner (C → X) band systems of H2 and Meinel (A → X), (B → A) and (B → X) band systems of OH are investigated. For radiative recombination, transitions between
H2+ (X) and H2(X), and between OH+(X, a, A, b, and c) and OH(X) are considered. Transition probabilities and recombination rate coefficients are calculated
as a function of temperature in the range 1500–15 000 K. 相似文献
2.
R. Riahi Ph. Teulet Z. Ben Lakhdar A. Gleizes 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,56(1):61-66
The weighted total cross section (WTCS) theory has been applied to the
electron-H2 collision to obtain excitation, ionisation and dissociation
cross section and rate coefficients of the X 1Sg+^{1}\!\Sigma _{g}^{+}, c
3Pu^{3}\!\Pi _{u}, a 3Sg+^{3}\!\Sigma _{g}^{+}, e $^{3}\!\Sigma
_{u}^{+}$^{3}\!\Sigma
_{u}^{+} and B′
1Su+^{1}\!\Sigma _{u}^{+} states. Calculation has
been performed in the temperature range 1500 K–15000 K. Rate coefficients
are calculated from WTCS assuming Maxwellian energy distribution functions
for electrons and heavy particles. Thermal equilibrium results are presented
and fitting parameters (a, b and c) are given for each reaction rate
coefficient: k(θ) = a (θb)
exp(-c/θ). 相似文献
3.
V.M. Khulugurov V.N. Salomatov I.M. Kalogeras A. Vassilikou-Dova I. Christakis 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(1):91-101
Thermally Stimulated Depolarisation Current (TSDC) and optical methods are applied to a range of alkali-fluoride crystals
in order to establish a model for the stable F
2
+
- like colour centres in LiF:OH-. The experimental results for LiF:OH- suggest that the OH- defects are partially destroyed under ionising irradiation or during crystal growth. The low-temperature dielectric relaxation
signals in LiF:OH- and LiF:Mg2+,OH- are attributed to highly interacting hydroxide ions and products of their destruction located in extended lattice defects.
In LiF:OH-, in contrast to other alkali halides, the results advocate for a defect-structure model, which considers a neutral defect
(ND, probably O2 or H2) sited at the anion vacancy of the O2--V
a
+
dipole and which possibly is the “nucleus” for the F
2
+
centre. The proposed F
2
+
(ND, O-) model seems to better explain the dielectric results, compared to the older F
2
+
(O2-) and F
2
+
(O-) models. The estimate for the electric dipole moment derived from the experimental TSDC bands, gives a value for the F
2
+
- like centre in LiF:OH- between those of the F
2
+
(O-) and F
2
+
(O2-) defects, in good agreement with the proposed F
2
+
(ND,O-) model. The reduction of the activation energy barrier of the (re)orientation process of the Mg2+V
c
-
(OH-) complexes in LiF:Mg2+,OH-, and the low-temperature shift of their TSDC band, compared to the single Mg
2
+
V
c
-
peak in LiF:Mg2+, are tentatively ascribed to an increase in the crystal-lattice parameters owing to the presence of OH- and/or products of its destruction.
Received 31 August 2001 / Received in final form 30 March 2002 Published online 9 July 2002 相似文献
4.
《The European Physical Journal C - Particles and Fields》2007,49(2):395-410
Measurements of inclusive production of the Λ, Ξ- and Ξ*(1530) baryons in two-photon collisions with the L3 detector at LEP are presented. The inclusive differential cross sections
for Λ and Ξ- are measured as a function of the baryon transverse momentum, pt, and pseudo-rapidity, η. The mean number of Λ, Ξ- and Ξ*(1530) baryons per hadronic two-photon event is determined in the kinematic range 0.4 GeV<pt<2.5 GeV, |η|<1.2. Overall agreement with the theoretical models and Monte Carlo predictions is observed. A search for inclusive
production of the pentaquark θ+(1540) in two-photon collisions through the decay θ+→pK0
S is also presented. No evidence for production of this state is found. 相似文献
5.
6.
M. Bertolus V. Brenner P. Millié 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(3):387-394
An ab initio study of the Nan(OH)n, Nan(OH)n-1
+, Agn(OH)n, and Agn(OH)n-1
+ clusters with n up to four is presented. The results of this study show that, in accordance with experimental observations, the sodium hydroxide
clusters are almost purely ionic, while the Ag-O bond exhibits a significant covalent character. The perturbation caused by
the non-spherical OH- group relatively to an atomic anion, as well as the influence on structures and energies of the covalent character of the
metal-oxygen bond are determined. The appearance of metal-metal bonds in the silver hydroxide clusters is also discussed.
Finally, the theoretical results obtained on the Na-OH clusters are compared to experimental results available on the dissociation
of the Nan(OH)n-1
+ clusters.
Received 9 August 1999 and Received in final form 1st December 1999 相似文献
7.
R. Muhida M. David M. M. Rahman W. A. Diño H. Nakanishi H. Kasai K. Fukutani T. Okano 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(1):99-101
We investigate the molecular orientation dependence of the (o)rtho-(p)ara H2 conversion on Fe(OH)3 cluster. Taking Fermi's contact interaction as perturbation, we find that the o-p H2 conversion yield for the molecular orientation angle θ= 10○ with respect to the surface normal is larger than that for θ= 70○. 相似文献
8.
A. Kanaev L. Museur F. Edery T. Laarmann T. Möller 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(2):261-268
We have studied the fluorescence of electronically excited OH*, H* and H2O+* dissociation fragments after VUV excitation ( h
ν≥11.6
eV) of rare-gas clusters (Rg = Ne, Ar) doped with H2O molecules. In contrast to a free molecule, where Balmer H-series dominate the UV-visible spectra, only the OH
*
(
A
2
Σ
+
↦
X
2
Π) emission band is observed in neon clusters. No emission of excited water ions has been observed. We find that while higher
excitation energies (Ne vs. Ar) induce higher vibrational excitation of the OH*
(
A
) fragment, the rotational temperature is lower. This effect is attributed to the difference in the geometric position of the
H2O molecule on the surface or inside the Rg-cluster. The rotational relaxation in neon clusters is rapid while the vibrational
relaxation is slow because of the coupling with the low energy matrix phonons.
Received 7 March 2002 / Received in final form 27 May 2002 Published online 19 July 2002 相似文献
9.
Hollow cathode (HC) lasers usually operate in a single axial mode without any optical selection. This is attributed to the
large homogeneous linewidth of the gain curve due to the relatively high filling pressure of these lasers. Collisional and
Doppler broadening (ΔνC and ΔνD) of the Cd+ 636 nm and Cd+ 538 nm lines (laser transitions of the HeCd+ laser) excited in a HC discharge tube were determined using a Fabry–Perot interferometer technique. It was found that in
the pressure range 7–25 mbar ΔνD was nearly constant, while, as expected, ΔνC increased linearly with pressure. The broadening constants were α(636 nm)= (47±2) MHz/mbarand α(538 nm)=(11.8±0.5) MHz/mbar.
The first constant is large enough to explain single-mode operation of the red HeCd+ laser; but in the case of the green laser, the exact reason for the single-mode operation remained unclear.
Received: 23 November 2000 / Revised version: 30 March 2001 / Published online: 7 June 2001 相似文献
10.
We perform DFT calculations to investigate the redox and formate mechanisms of water–gas-shift (WGS) reaction on Au/CeO2 catalysts. In the redox mechanism, we analyze all the key elementary steps and find that the OH cleavage is the key step. Three possible pathways of OH cleavage are calculated: (1) OHad″+*′→Had′+Oad″; (2) Had′+OHad″→H2(g)+Oad″+*′; and (3) OHad″+OHad″→2Oad″+H2(g) (*′: the free adsorption sites on the oxides; ad′: adsorption on the metal; ad″: adsorption on the oxide, respectively). In the formate mechanism, we identify all the possible pathways for the formation and decomposition of surface formates in the WGS reaction. It is found that there is a shortcoming in the redox and formate mechanisms which is related to surface oxygen reproduction. Four possible pathways for producing surface oxygen are studied, and all the barriers of the four pathways are more than 1 eV. Our results suggest that the processes to reproduce surface oxygen in the reaction circle are not kinetically easy. 相似文献
11.
Apatite is a mineral with general formula M10(XO4)6Z2, where M are metallic elements such as Li+, Na+, K+, Ca2+, Sr2+, Ba2+, Ln3+ etc.; X=P, V, S, Si, Ge, Re, Cr etc; Z=F−, Cl−, I−, OH−, O2−, S2− etc. Some materials with apatite structure (S.G. P63/m) exhibit quite high cationic (Li+, H+ etc.) and/or anionic (F−, Cl− etc.) conduction. Recently, it was reported that some rare earth silicates, e.g., La10(SiO4)6O3, exhibit quite high oxide-ion conductivity. In this paper, we discuss chemical composition, structure, synthetic procedure
and ionic conduction of apatite-type materials. Recent improvements are briefly reviewed. High ionic conductivity has been
observed for both cation deficient, oxygen stoichiometric La9.33(SiO4)6O2 and cation stoichiometric, oxygen excess La10(SiO4)6O3 compositions. Grain boundary conductivity is usually low, which tends to dominate the impedance response. The resistance,
particularly the grain boundary resistance is also found to depend on pO2.
Paper presented at the 7th Euroconference on Ionics, Calcatoggio, Corsica, France, Oct. 1–7, 2000. 相似文献
12.
M. L. Du 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(3):533-536
We derive a formula using closed-orbit theory for the photodetachment cross-section of H- in the presence of a static electric field when there is an arbitrary angle θL between the laser polarization direction and the static electric field. This formula generalizes the previous result for
laser polarization parallel to the static electric field, the effect of laser polarization direction appears as a factor cos2(θL) in the amplitude of the oscillation. A photodetachment cross-section formula valid above and below detachment threshold
is proposed. 相似文献
13.
Hydroxyl tagging velocimetry (HTV) in experimental air flows 总被引:1,自引:0,他引:1
L.A. Ribarov J.A. Wehrmeyer R.W. Pitz R.A. Yetter 《Applied physics. B, Lasers and optics》2002,74(2):175-183
The new nonintrusive instantaneous molecular flow tagging method, hydroxyl tagging velocimetry (HTV), previously demonstrated
only for high-temperature reacting flows, is now demonstrated in low-temperature (300 K) ambient air flowfields. Single-photon
photodissociation of ground-state H2O by a ∼193-nm ArF excimer laser ‘writes’ very long grid lines (>50 mm) of superequilibrium OH and H photoproducts in a room
air flowfield due to the presence of ambient H2O vapor. After displacement, the positions of the OH tag lines are revealed through fluorescence caused by A2Σ+ (ν′=0)?X2Πi (ν′′=0) OH excitation using a pulsed frequency-doubled dye laser with an operating output wavelength of ∼308 nm. The dye ‘read’
laser accesses the strong Q1(1) line, compensating for the relatively weak 193-nm absorption of room-temperature H2O. The weak absorption of ground vibrational state H2O has previously precluded the use of HTV at low temperatures, since previous HTV systems relied on a KrF excimer ‘read’ laser
that could only access a weak (3?0) OH transition. The instantaneous velocity field is determined by time-of-flight analysis.
HTV tag lifetime comparisons between experimental results and theoretical predictions are discussed. Multiple-line tag grids
are shown displaced due to an experimental air flowfield, thus providing 2-D multipoint velocity information. Due to the instantaneous
nature of the HTV tag formation, HTV is particularly suitable for, but not limited to, a variety of fast flowfield applications
including nonreacting base flows for high-speed projectiles and low-temperature hypersonic external or internal flows.
Received: 3 July 2001 / Revised version: 6 November 2001 / Published online: 17 January 2002 相似文献
14.
T. Iino K. Ohashi K. Inoue K. Judai N. Nishi H. Sekiya 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):37-40
Vibrational spectra of mass-selected
Ag+(H2O)n ions are measured by infrared photodissociation
spectroscopy and analyzed with the aid of density functional theory
calculations. Hydrogen bonding between H2O molecules is found to be
absent for cold Ag+(H2O)3, but detected for
Ag+(H2O)4 through characteristic changes in the position and
intensity of OH-stretching transitions. The third H2O coordinates
directly to Ag+, but the fourth H2O prefers solvation through
hydrogen bonding. The preference of the tri-coordinated form is attributed
to the inefficient 5s–4d hybridization in Ag+, in contrast to the
efficient 4s–3d hybridization in Cu+. For Ag+(H2O)4,
however, di-coordinated isomers are identified in addition to the
tri-coordinated one. 相似文献
15.
The infrared and Raman spectra of solid CsSbF 5OH and CsSbF 4(OH)2 have been studied to determine the effect of replacing one or more F--ions by OH--ions in the SbF-6-ion. The results have been obtained in the frequency ranges where the Sb-F and Sb-OH stretching modes are known to occur. The spectra are in agreement with a low site symmetry for the SbF 5OH--ion in CsSbF 5OH but are largely inconclusive as to whether the OH-groups in CsSbF 4(OH)2 have cis- or trans-symmetry. 相似文献
16.
F. Schümann S. Zavatarelli L. Gialanella U. Greife M. Junker D. Rogalla C. Rolfs F. Strieder H.P. Trautvetter 《The European Physical Journal A - Hadrons and Nuclei》1998,2(4):337-342
Abstact: The elastic scattering cross sections, σ (E,θ), for the systems He+Ta and He+W have been measured at θlab=165° and E
lab=76.1 keV to 3.988 MeV using targets with a thickness of a few atomic layers. The results are smaller than the results given
by the Rutherford scattering law, σR(E,θ), due to the effects of electron screening and can be described by σ(E,θ)/σR(E,θ)=(1+Ue/E)−1, where U
e is an atomic screening potential energy. The deduced average value, U
e=28 ± 3 keV, is consistent with the Moliére- and Lenz-Jensen-models as well as electron binding energies.
Received: 25 May 1998 相似文献
17.
F. Liu W. Wang W. Zheng Y. Wang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(3):435-440
In this study, spatially resolved measurements of the
emission intensity of OH (A2Σ↦X2Π, 0-0) and the
vibrational temperature of N2 (C) have been performed during a positive
pulsed streamer discharge with a wire-plate electrode configuration at
atmospheric pressure. The effects of pulse peak voltage, pulse repetition
rate and the added O2 flow rate on the spatial distributions of the
emission intensity of OH (A2Σ↦X2Π, 0-0) and the
vibrational temperatures of N2 (C) perpendicular to the wire in the
direction towards the plate (in the radial direction) are investigated. It
has been found that the emission intensity of OH (A2Σ↦X2Π, 0-0) increases with increasing pulse peak voltage and pulse
repetition rate and decreases with increasing the distance from the wire
electrode. When the different oxygen flows are added in N2 and H2O
mixture gas, the emission intensity of OH (A2Σ↦X2Π, 0-0) decreases with increasing the flow rate of oxygen. The
vibrational temperature of N2 (C) is nearly independent of pulsed peak
voltage and pulsed repetition rate, but increases with increasing the added
O2 flow rate and keeps almost constant in the radial direction under
the present experimental conditions. This measurement plays a crucial role
in understanding the discharge characters of pulsed streamer discharge and
establishing the molecule reaction dynamics model of pulsed streamer
discharge. 相似文献
18.
RUAN Ying CAO Chongde & WEI Bingbo Department of Applied Physics Northwestern Polytechnical University Xi’an China 《中国科学G辑(英文版)》2004,47(6):717-728
~~Rapid growth of ternary eutectic un der high undercooling conditions1.Offerman, S.E., Dijk, N.H., Sietsma, J.et al., Grain nucleation and growth during phase transformations, Science, 2002, 298: 1003-1005.
2.Warren, J.A., Langer, J.S., Prediction of dendritic spacings in a directional-solidification experiment, Phys.Rev.E, 1993, 47: 2702-2712.
3.Cao, C.D., Wang, N., Wei, B., Containerless rapid solidification of undercooled Cu-Co peritectic alloys, Science in China, Ser.A, … 相似文献
19.
The chemical composition of ultrafine amorphous Fe−B powders prepared by a chemical reduction depends on the mixed molar ratio
of KBH4 to Fe ions. We propose the following reaction processes for the formation of ultrafine Fe−B powders: (1) 4Fe2++2BH4−+6OH−→2Fe2B+6H2O+H2 and (2) 4Fe2++2BH4−+7OH−→2Fe3B+Fe+BO2+5H2O+5/2H2. 相似文献
20.
《The European Physical Journal C - Particles and Fields》2008,53(1):1-14
We report measurements of charmonia produced in two-photon collisions and decaying to four-meson final states, where the meson
is either a charged pion or a charged kaon. The analysis is based on a 395 fb-1 data sample accumulated with the Belle detector at the KEKB electron–positron collider. We observe signals for the three
C-even charmonia ηc(1S), χc0(1P) and χc2(1P) in the π+π-π+π-, K+K-π+π- and K+K-K+K- decay modes. No clear signals for ηc(2S) production are found in these decay modes. We have also studied resonant structures in charmonium decays to two-body
intermediate meson resonances. We report the products of the two-photon decay width and the branching fractions, , for each of the charmonium decay modes.
PACS 13.25.Gv; 13.66.Bc; 14.40.Gx 相似文献